1. Field of the Invention
The present invention relates to a notebook information processor, and projective transformation parameter calculating method.
2. Description of the Related Art
With a notebook information processor such as conventional PDA terminal and laptop type PC, by way of example, when a user such as a businessman wants to scan a document such as a paper document not at his desk in an office with a well-equipped environment but at a meeting, when visiting a customer, and in a hotel of a business trip destination, it is required to additionally bring a portable scanner or a digital camera.
When additionally bringing the portable scanner, a general commercially available notebook information processor and a portable scanner weigh about 1 to 2 kg and 1.4 kg, respectively, so that they weigh about 3 kg in total and are too heavy for the user to bring. In addition, the user has to keep an installation area of both the notebook information processor and the scanner when scanning.
Therefore, although the digital camera is often used in place of the portable scanner without bringing the latter, in this case, however, it is difficult to straightforwardly photograph the document without using a tripod or the like, so that it is required to convert the document photographed by the digital camera as if this is straightforwardly photographed.
That is to say, when using the notebook information processor such as a notebook personal computer and the digital camera in place of the image scanner, it is required to use a technique to correct distortion of a viewpoint when photographing by an existing projective transformation technique.
Conventionally, there is a technique to calculate a projective transformation parameter for performing the projective transformation on the document as if this is straightforwardly photographed in an over head projector (OHP) type photographing device or the like.
For example, the OHP-type photographing device disclosed in JP-A-2006-74512 uses the rectangle of the outline of the seat of which shape is known as the reference polygon, and compares the rectangle with the rectangle identified by the contour of the seat image, thereby obtaining the projective transformation parameter.
However, in the conventional projective transformation technique (such as JP-A-2006-74512), for example, the rectangular seat of which four corners are square is required as the rectangle used for calculating the projective transformation parameter, and there is a problem that when the four corners of the seat are not square and the seat is not rectangular, the rectangular figure of which four corners are square is required to be separately provided or the apex signs such as the corner marks are required to be drawn on the seat so as to detect the coordinates of the four corners of the seat.